Metalloaluminophosphate (MeAPO) molecular sieves contain lattice metal in tetrahedral coordination with oxygen atoms in a three-dimensional microporous crystal framework structure of [SiO2], [AlO2], and [PO2] corner sharing tetrahedral units. The [PO2] tetrahedral units are provided by a variety of compositions including phosphoric acid, organic phosphates such as triethyl phosphate, and aluminophosphates. The [AlO2] tetrahedral units are provided by a variety of compositions including aluminum alkoxides such as aluminum isopropoxide, aluminum phosphates, aluminum hydroxide, sodium aluminate, and pseudoboehmite. The [SiO2] tetrahedral units are provided by a variety of compositions including silica sols and silicon alkoxides such as tetraethylorthosilicate and fumed silica. The metal tetrahedral units are provided by a variety of compositions including Mg, Mn, Zn, and Co compounds.
SAPO-34 and SAPO-18 have been reported as suitable catalysts for light olefin production from methanol. SAPO-34 belongs to the family of molecular sieves having the structure type of the zeolitic mineral chabazite (CHA). The preparation and characterization of SAPO-34 has been reported in several publications, including U.S. Pat. No. 4,440,871; J. Chen et al. in “Studies in Surface Science and Catalysis”, Vol. 84, pp. 1731-1738; U.S. Pat. No. 5,279,810; J. Chen et al. in “Journal of Physical Chemistry”, Vol. 98, pp. 10216-10224, 1994; J. Chen et al. in “Catalysis Letters”, Vol. 28, pp. 241-248, 1994; A. M. Prakash et al. in “Journal of the Chemical Society, Faraday Transactions,” Vol. 90(15), pp. 2291-2296, 1994; Yan Xu et al. in “Journal of the Chemical Society, Faraday Transactions” vol. 86(2), pp. 425-429, 1990, all of which are herein fully incorporated by reference.
U.S. Pat. No. 6,334,994, incorporated herein by reference, discloses a silicoaluminophosphate molecular sieve, referred to as RUW-19, which is said to be an AEI/CHA mixed phase composition. In particular, RUW-19 is reported as having peaks characteristic of both CHA and AEI framework type molecular sieves, except that the broad feature centered at about 16.9 (2θ) in RUW-19 replaces the pair of reflections centered at about 17.0 (2θ) in AEI materials and RUW-19 does not have the reflections associated with CHA materials centered at 2θ values of 17.8 and 24.8. DIFFaX analysis of the X-ray diffraction pattern of RUW-19 as produced in Examples 1, 2, and 3 of U.S. Pat. No. 6,334,994 indicates that these materials are characterized by single intergrown phases of AEI and CHA framework type molecular sieves with AEI/CHA ratios of about 60/40, 65/35, and 70/30, respectively. Throughout this description, the XRD reflection values are referred to as (2θ), which is synonymous to the expression “degrees 2θ.”
U.S. Pat. No. 6,812,372, incorporated herein by reference, discloses a silicoaluminophosphate molecular sieve, comprising at least one intergrown phase of molecular sieves having AEI and CHA framework types, wherein said intergrown phase has an AEI/CHA ratio of from about 5/95 to 40/60 as determined by DIFFaX analysis, using the powder X-ray diffraction pattern of a calcined sample of said metalloaluminophosphate molecular sieve.
U.S. patent application Ser. Nos. 10/092,792 and 10/995,870 disclose a silicoaluminophosphate molecular sieve comprising at least one intergrown phase of molecular sieves having AEI and CHA framework types, wherein the intergrown phase has an AEI/CHA ratio of from about 5/95 to 40/60 as determined by DIFFaX analysis, using the powder X-ray diffraction pattern of a calcined sample of the metalloaluminophosphate molecular sieve. It also relates to methods for its preparation and to its use in the catalytic conversion of methanol to olefins.
U.S. patent application Ser. No. 10/425,587 discloses methods and compositions of synthesis mixtures for the synthesis of aluminophosphates and silicoaluminophosphate molecular sieves, which enable the control and adjustment of the crystal particle size of aluminophosphates and silicoaluminophosphate molecular sieves. The synthesis mixture compositions used have two or more organic templates present at a molar ratio of total template to aluminum of ≦1.25; such a synthesis mixture is susceptible to control of product particle size through variation in the amount of seeds used in the synthesis.
U.S. Pat. No. 4,567,029 discloses a crystalline microporous metal aluminophosphate compositions containing as lattice constituents in addition to AlO2 and PO2 structure units, one or a mixture of two or more of the metals Mg, Mn, Co, and Zn in tetrahedral coordination with oxygen atoms (MAPO).
U.S. Pat. No. 5,912,393 discloses a catalyst for converting methanol to light olefins. The catalyst is a metalloaluminophosphate molecular sieve having the empirical formula (ELxAlyPz)O2 where EL is a metal such as silicon or magnesium and x, y, and z are the mole fractions of EL, Al, and P respectively. The molecular sieve has a crystal morphology in which the average smallest crystal dimension is at least 0.1 microns. Use of this catalyst gives a product with a larger amount of ethylene versus propylene.
EP Patent Application No. 1,142,833 discloses a class of microporous metalloaluminophosphate molecular sieves (MeAPSOs) and the method of their fast preparation. These molecular sieves can be represented by the empirical formula on an anhydrous basis: mR.(MqSixAlyPz)O2, wherein “R” represents the templating agent presented in the intracrystalline pore system; “m” is the molar amount of “R” per mole of (MqSixAlyPz)O2 and has a value from 0.01 to 8.00; “M” represents at least one metal element; “q”, “x”, “y”, and “z” represent the molar fractions of metal, silicon, aluminum, and phosphorus respectively, whose variations are q=0−0.98, x=0−0.98, y=0.01−0.60, z=0.01−0.60, and q+x+y+z=1. The crystallization time of the synthesis is 0.5-12 hours, which is defined as the method of fast preparation.